The University of Minnesota is joining a national movement requiring students to obtain "affirmative consent" from their sex partners or risk being ­disciplined for sexual assault.

The policy change, sometimes known as the "yes means yes" rule, has been sweeping college campuses across the country since California passed the first such law last year.

The U's new rule, which is poised to take effect this month after a 30-day comment period, says that sex is OK only if both parties express consent through "clear and unambiguous words or actions." Absent that, it would fit the U's ­definition of sexual assault.

So far, the plan has prompted little dissent at the U. But nationally, critics have derided such policies as absurd and dangerous, particularly when it comes to protecting the rights of the accused.

"Once that accusation has been made, it's somehow up to the accused person to prove they did have consent," said Robert Shibley, executive director of the Foundation for Individual Rights in Education (FIRE), a civil liberties group in Philadelphia. "What that means is that they're guilty until proven innocent."

The campaign for affirmative consent rules has been fueled by a tidal wave of outrage about campus rape, and concern that college officials haven't done enough to crack down on sexual assault.

"It's spreading pretty fast," said Alison Berke Morano, a Florida political strategist who helped launch the "Affirmative Consent Project" in February. "It's been faster than I've seen other movements."

The Affirmative Consent Project, a national advocacy group, distributes a consent form (below) that college students can sign before sex.

Just a year ago, ­California passed the first such law, requiring colleges to adopt the new language.

Since then, lawmakers in more than a dozen states, including Minnesota, have introduced similar legislation (the Minnesota bill failed to make it into law this spring).

Meanwhile, many colleges and universities have been changing the language voluntarily.

At the same time, Morano's organization has started distributing "consent contracts" that students can sign, partly as a tactic to get the conversation started.

What's an innocent kiss?

The problem, Morano said, is that the burden in cases of alleged sexual assault has been on victims to prove they were victimized.

"The accuser is always the one who has to prove that it happened," she said.

Joelle Stangler, student body president at the U, said that's why students themselves have been demanding the change.

"Really, there's been a lack of due process for victims forever," she said. "We're now shifting and rebalancing, where both parties need to be able to demonstrate there was consent."

Kimberly Hewitt, who's in charge of investigating sexual assault complaints at the U, said the new rule could help clarify what is often a murky situation.

She noted that colleges are required by federal regulations to investigate all such allegations, whether or not they're reported to the police.

"Most sexual assault investigations that we do … are complicated," said Hewitt, vice president of equal opportunity and affirmative action. "It's a college campus, so in many cases there's alcohol involved. People may or may not be in a relationship … They're all individual, and they're all really complex."

The rule change, she said, might make the investigator's job a bit easier.

"It could be more clear to say, 'Tell me how you understood that you had permission to do this?' " she said.

To Shibley, a civil liberties lawyer, that's precisely the problem.

"They're asking the accused to recall or somehow convince the tribunal that they did get consent," he said. Without a witness or a video, he noted, that may be impossible.

"The person who's accused is left with effectively no defense," he said. "That's a very dangerous standard to use to determine that somebody's a rapist."

At the same time, critics say that the affirmative consent rule vastly expands what constitutes a punishable offense, which potentially can lead to expulsion.

Redefines sexual encounters

Columnist Cathy Young, writing about the California affirmative consent law on reason.com, said it "essentially redefines some 95 percent of human sexual encounters as rape."

Even something as innocuous as sneaking up on one's partner with a kiss, critics say, could run afoul of the guidelines.

Shibley wonders how the U would enforce one provision, which requires that "consent must be present throughout the sexual activity."

"Do they mean each stage?" he asks. "Do they mean kissing? … If I, as a First Amendment attorney, cannot figure this out, there's no way an 18-year-old student is going to figure it out."

But Karen Hanson, the U's provost, said she thinks the fears are overblown.

"We've still got tons of due process about these issues," she said, including the right to appeal. "I actually don't think there's any shifting of the burden of proof."

Hanson, who serves on the presidential policy committee that endorsed the new approach, said she sees it mainly as a teaching tool. "We're in the education business," she said. "What this is trying to get students to understand is that silence doesn't equal consent."

Reading body language

Stangler said there's a clear consensus on campus in favor of the new policy. And a sampling of students, taking a break between classes last week, showed solid support among both men and women.

"I think it absolutely needs to be in policy," said Romy Ackerberg, a 22-year-old senior. In fact, she said she'd like it to be even tougher, insisting on verbal consent. "Anybody can interpret body language in any way," she said.

Troy Kariniemi, another 22-year-old senior, said he thought it "would do a lot of good," and added: "I don't have any problems with adhering to that kind of rule."

Anders Koskinen, chair of the campus Republicans, said he too has heard little concern. But he suspects skeptics may be biting their tongues.

"If you voice concern — reasonable concern about the process — that's interpreted sometimes as you don't care about actual victims," he said.

Shibley said that may account for the muted response across the country.

"There's a real sense out there that there's a crisis on campus when it comes to sexual assault," he said. "No one wants to be the person who looks like they're out there apologizing for those people."

Advocates say the new consent policies are worth a try, though some admit it's still an open question whether they will make campuses safer.

"We don't know that yet," Morano said. "We're going to find out."

Maura Lerner • 612-673-7384